Remove trailing \0 from values read from ppc64le device-tree.
Remove trailing \0 from values read from ppc64le device-tree.

For example:
$ sudo od -t cx1 /proc/device-tree/system-id
0000000   I   B   M   ,   0   6   7   8   B   2   3   0   0  \0
         49  42  4d  2c  30  36  37  38  42  32  33  30  30  00

linux-on-ibm-z/cadvisor,linux-on-ibm-z/cadvisor,linux-on-ibm-z/cadvisor